Abstract: :
Purpose: To analyze the corneal thickness obtained by Orbscanand ultrasonic pachymeter.Methods: We prospectively studied the corneal thickness in 300normal eyes of 150 patients with the Orbscan II (Bausch &Lomb) and Tomey SP–2000 ultrasonic pachymeter, includingeyes with ametropia. We used default setting for both devices.Three central ultrasonic readings were averaged to give a singlevalue. For each eye and for both devices two measurements weresuccessively recorded to calculate the reproducibility. Withthe Orbscan we analyzed the central and peripheral (9 locations)pachymetry, as well as the thinnest point. The localizationof the thinnest point according to the corneal apex was analyzedusing cartesian coordinates.Results: Central pachymetric measurements of both eyes stronglycorrelated (rs= 0.98, p<0.001 ultrasonic pachymetry; rs=0.97, p<0.001, Orbscan pachymetry). For the central pachymetricmeasurements both methods strongly correlated (rs= 0.97, p<0.001)and the precision of both methods was not significantly different(p=0.14). The difference between 2 successive measurements wasapproximatively 5 µm or 1%. The distance from the cornealthinnest point to the apex was 0.63 + 0.25 mm. The thinnestpoint was most commonly located in the inferotemporal quadrant(66%), followed by the superotemporal (24%), inferonasal (6%),and superonasal (4%) quadrants. The central pachymetry is notcorrelated with the subjective spherical equivalent but withthe age (rs= 0.28; p<0.001).Conclusions: The corneal thickness analyzed with the ultrasonicpachymeter and Orbscan provided high reproducibility. Therewas a significant correlation between the results obtained byboth techniques. Contrary to the ultrasonic pachymeters theOrbscan simultaneously measures several thousand points includingthe thinnest point and provides a colour–coded thicknessmap without physical contact.